Refractory compact manufacture



7 NOW 1963 E. L. LITTLE, JR.. ETAL 3,110,091

REFRACTORY COMPACT MANUFACTURE Filed Dec. 23, 1960 FIG. 4

H62 INVENTORS ERNEST L. LITTLE, JR. HARRY J. McCAULEY FRANK J. PENOZA BYWan :7

ATTORNEY United States Patent 3,110,091 REFRACTORY COMPACT MANUFACTUREErnest L. Little, Jr., Harry J. McCauley, and Frank J.

Penoza, Wilmington, DeL, assignors toE. I. du Pont de Nemonrs andCompany, Wilmington, Del, 21 corporation of Delaware Filed Dec. 23,196i), Ser. No. 73,088 8 Claims. (Cl. 29-1825) This invention relates tothe manufacture of molybdenum-nitrogen-silicon alloy compacts, andparticularly to a method and composition for the manufacture of selectedmolybdenum-nitrogen-silicon alloy compacts in the form of shaped objectshaving high inherent lubricity and improved toughness such as isrequired in hot metal extrusion die nibs, bearings and other articles asto which there is metal-to-metal contact at elevated temperatures.

There is a steadily growing need for metal-forming apparatus, bearingsand other devices exhibiting a low coeflicient of friction coupled withhigh temperature and erosion resistance and resort has been had to avariety of refractory materials for this purpose. However, there hasbeen a marked deficiency with respect to inherent lubricity, especially,by which is meant the slipperiness displayed by a material. In addition,it has proved very difiicult, if not impossible, to form thesesubstances with apertures such as bores, partial bores or even generallyconcave surfaces, due to inherent brittleness, hardness, abrasivenessand other unfavorable characteristics, and this is particularly truewhere the apertures must be formed to high dimensional precision andare, in service subjected to terrific loading stresses and temperatures,such as exist with hot metal extrusion die nibs and, in extreme cases,with bearings. Finally, most refractory materials are low in tensilestrength and are difficult to mount in supports giving the necessaryback-up strength.

It is an object of this invention to provide a composition and methodfor the manufacture of improved compacts of high inherent lubricity andtoughness consisting mainly of molybdenum, silicon, nitrogen and atleast one of the three metal oxides ZrO ZnO and Cr O It is anotherobject of this invention to provide a modified nitrogen-containingmolybdenum silicide compact which is amenable to the inclusion ofapertures in the structure. It is a further object of this invention toprovide a composition which is adapted to the fabrication of hot metalextrusion die nibs, bearings and similar structures having highdimensional stability and relatively low cost. The manner in which theseand other objects of this invention are attained will become apparentfrom the following detailed description and the drawings, in which:

FIG. 1 is a vertical sectional view of a preferred aspressed shape ofcompact for the manufacture of a die nib according to this invention,wherein cross-hatching has been partly omitted to better show theseveral dimensional attributes,

FIG. 1a is a vertical sectional view of the compact of FIG. 1 in theas-finished form of a die nib and in condition to be mounted in asuitable holder for metal extrusion, the flare of the discharge openingbeing somewhat exaggerated to show this detail,

FIG. 2 is a vertical sectional view of a preferred embodiment ofgraphite die mold adapted to the manufacture of compacts of the designshown in FIG. 1,

FIG. 3 is a fragmentary view in transverse section through the extrusionthroat of a special design of die nib adapted to form fluted metal rodsby hot extrusion, and

FIG. 4 is a sketch copying a small section of a 100 0 photomicrograph ofan etched metallographic specimen "ice cut from a typical MoNSiZrO hotmetal extrusion die.

Generally, this invention comprises a composition useful in thefabrication of compacts which have a high inherent lubricity andimproved toughness Consisting essentially of 2053% Si, 40-65% M0, 119% Nand from about 5-20% of a metal oxide taken from the group consisting ofZrO ZnO and Cr O and also a method of manufacturing such compacts.

Ne have found (refer to copending US. application S.N. 78,102 filed ofeven date herewith) that certain trimetal systems, such as Fe--Mo-Si,FeSiTi and MoNSi-Ti, are improved substantially in physical propertiesby the addition thereto of one or more of the specific metal oxides ZrOZnO and Cr O followed by sintering of the intimately mixed ingredientsby conjoint use of heat and pressure. Our investigation has now shownthat the bi-metal system MHi containing chemically combined N (which isdisclosed in US. application S.N. 793,922), at least within a criticalcomposition range, is also benefited by inclusion of one or more of themetal oxides hereinbefore mentioned, and it is to this advance that thisapplication is directed.

It is ditficult to isolate the most important result of metal oxideaddition, since the characteristics of the manufactured product must beappraised as a composite on the basis of use tests. Nevertheless, itappears that the metal oxides enhance the lubricity of the compacts and,at the same time, serve a useful function in the prevention of crackingor disintegration during the high pressure consolidation necessary tothe production of high density compacts of good strength and erosionresistance.

Moreover, the metal oxide additive is advantageous also from thestandpoint of aperture formation in the compacts, and this is true forboth the situation wherein the apertures are molded, at least in therough, during the consolidation by which the compact itself is formed orwhere the apertures are formed in the compact by later machiningoperations. Finally, the metal oxide additives appear to impart atoughness to the compacts which enable them to withstand stressesimposed on them during pressing or shrinking occurring in the mountingof the compacts within associated support housings.

This invention is hereinafter described with particular reference to themanufacture of hot metal extrusion die nibs, because the fabrication ofthese devices requires, to an exceptional degree, the overcoming ofproblems of precise dimensional control, the formation of apertures inthe compacts and the like which are common to other structures such asbearings and similar apertured devices as to which this invention isalso applicable. In all cases, powdered metallurgy techniques areemployed in the manufacture, the compositions of this inventionconsisting in original, unalloyed, unsintered form of metal powdermixtures which are, however, converted to alloys during the sintering byconjoint use of heat and pressure. Thereafter, for use as die nibs, thecompacts are mounted in suitable support housings, such as described incopending U.S. application S.N. 78,165, filed of even date herewith,which confer uniform high strength support for the compositions over thewide temperature ranges in which hot metal extrusions are conducted.

Metal forming by the extrusion technique is particularly advantageousfrom the following standpoints: the ability to form relatively complexshapes in a single pass, easy change-over from one shape product toanother, short lead time in production, ease of design change, reducedWorking capital and increased processing yields. In addition, the dienibs of this invention make it possible to dispense with extrusionlubricants either entirely, or to a very great extent, which gives animproved product quality in terms of both surface finish and tolerance,as well as eliminates cleansing problems. 'It appears, also, that thenew die nibs make it possible to extrude new metals and alloys in newshapes never before achieved by the industry.

The ability to dispense with lubricants in metal extrusion is aparticularly important advance, since the use of such lubricants hasbeen hitherto considered to be almost axiomatic in the art. For metalswhich can be worked at temperatures under about 500 C., such as Al andMg, for example, hydrocarbon oils have been used as extrusionlubricants. However, for the higher temperatures required for theextrusion forming of copper, steel, ferrous alloys and refractory metalsthere is difficulty in finding a lubricant which possesses suitableviscosity and stability. Graphite is widely used for the coating of themetal feed input passages, which are referred to in the art as thecontainers, leading to the die nibs, and sometimes the die nibsthemselves; however, graphite does not provide the continuously movingfilm possessed by a fluid lubricant. Recently, molten glasses, moltensalts, clay-graphite mixtures and specially compounded greases haveaided metal extrussions in the higher temperature range above 1000 C.,but these have also been deficient, in that the lubricant film has notbeen continuously maintained and, where it has failed, there has beenobjectionable galling of the extrudate accom panied by accelerated anduneven wear on the die nibs. Lubricant failure in the extrusion of softmetals, such as aluminum, can oftentimes be tolerated from thestandpoint of die nib wear, because the nib life remains still quitelong; however, where steels, ferrous alloys and refractory metals arebeing extruded, the nib life is drastically reduced and is frequentlymeasured in terms of only 1-10 pushes per die nib.

The importance of die nibs of maximum resistance to erosion is evident,because the dimensional tolerance and surface finish of the extrudateproduct is directly dependent thereon. It is at least equally important,though, to eliminate lubricants in all extrusion work if at allpossible, since lubricants remaining on the product are a contaminantwhich must thereafter be removed by degreasing, or even by grit blastingand pickling in the case of glass lubricants, which is expensive,time-consuming, and frequently harmful to the product because ofcorrosion, oxidation promotion or the like. Finally, lubricant failurebecomes more serious where the extrudate product has fins, projections,sharp edges, re-entrant angles and other shape peculiarities, becausethe lubricant cannot readily adapt itself to accommodation of thesefeatures. The trend, however, is to produce by metal extrusion productswhich are increasingly complex in cross-sectional profile and thus thereis a clear neces-- sity for lubricant elimination in view of thisconsideration also.

The conversion of the powdered compositions to solid compacts ashereinafter described generally involves calorescence (i.e., anexothermic reaction characterized by an increase in temperature asevidenced by an increase in luminosity) that is induced when aconsiderable portion of the consolidated powder is heated to atemperature of at least 900 C. The internal temperature of the massduring this conversion reaches 1100-l600 C. When the spontaneous heatincrease due to calorescence is low, the temperature to achieveconversion must be raised by external heat application. The metal Si isso exothermic in its reaction with other metal constitutents that it cangenerate extreme heat, which sometimes even appears capable ofvaporizing some of the constituents. Accordingly, it is preferred thatat least a part of the Si be utilized according to this invention as acompound with some other element, e.g., as silicone nitride, molybdenumdisilicide, or the like. However, molybdenum can be utilized inelemental form.

The purity of commercial grade MoSi is generally about 99%, whereas thatof silicon nitride is typically 92%. Elemental molybdenum is availableat 99% purity, or even higher. We have found that compacts made from therelatively impure binary alloys have proved completely satisfactory inservice, even though there are appreciable quantities of inert diluents,e.g., Al, Mn, Ca, Mg, Cu and Ni present, either as elements or oxides.In general, it is preferred that these inert substances be below about5%, or even better, below 3% in the starting materials as received. Anadditional consideration is that the ball milling size reductionoperation inevitably adds a small amount of silica or alumina, andperhaps minor amounts of other substances as a consequence of attritionof the grinding elements.

In general, we have found that compositions in the range of about 20-53%Si, 4065% Mo, 1-19% N and from about 520% of a metal oxide taken fromthe group consisting of ZrO ZnO and Cr O are satisfactory for thepurposes of this invention. As taught in US. application S.N. 793,922hereinbefore referred to, it is often helpful to moisten the powder witha liquid, eg, Water, to assist in forming it to the desired shape.Aqueous solutions of sodium hydroxide containing a few percent, i.e.,1-5% NaOH are particularly desirable for this purpose. The small amountof sodium hydroxide contained in the composition after drying leads tothe formation of alloy objects having improved properties.

A typical composition according to this invention, ignoring therelatively small amounts of inerts present, is that made up from apowder containing 58.7 M0, 7.1 N, 34.2 Si, to which ZrO in the amount of10% by Weight is added.

This composition was formulated as follows: 250 gms. of molybdenumpowder (200 mesh), 500 gms. of MoSi powder (200 mesh) and 220 gms. ofsilicon nitride (-325 mesh) were milled together in a one-galloncapacity porcelain jar mill to which were added 3000 gms. of flintpebbles. A liquid additive consisting of 1000 cc. of benzene was addedto prevent compaction of the powder during the ball milling and the ballmill was operated for 72 hours at a speed of 40 r.p.m. The product wasthereafter dried for 16 hours in an air atmosphere in an electric ovenmaintained at C., after which it was screened through a 200 mesh sieve.

To the dried powder mixture hereinbefore described was added 108 gms. ofdry ZrO preground separately at substantially the same speed and for thesame time. The two powdered portions were intimately mixed together withthe aid of a conventional electrical 'blender, after which electronmicroscope examinations showed that there was obtained a homogeneousmixture wherein most particles were 1-3 microns in size, although anappreciahle number were below 1 micron and there were a few somewhatlarger, in the extreme case up to about 10 microns. Particle sizecontrol within this range is preferred for best results; however,acceptable products are obtained where the particle size is less thanabout 75 microns, of which at least 75% by weight are less than about 5microns. It will be understood that fluid energy mills, or otherdesigns, can be substituted for ball milling if desired.

The individual or co-mixed powders can be stored indefinitely in glassbottles provided with plastic caps Without deterioration; however, it ispreferred to store them in an air-conditioned room maintained at atemperature of about 24 C. and a relative humidity of about 40% tomaintain the physical handling properties unaltered, which is an aid inthe later manufacturing operations.

Turning now to extrusion die nib manufacture per se, a typical die nibhad the as-pressed shape of FIG. 1 and was thereafter finished to thefinal shape of FIG. 10, after which it was mounted in a suitable supporthousing and was then ready for use in metal extrusion. It will beunderstood that an extremely wide variety of die nib shapes can befabricated according to this invention, and that some shapes performbetter than others as regards specific metals to be extruded, reductionratios, rate of extrudate throughput, extrusion temperatures, whether ornot lubricants are used during the extrusion and many otherconsiderations. The design described is a highly eflective one and iswell-suited to hot metal extrusions.

The specific nib, tested as hereinafter described, measured, in thefinished form shown in FIG. 1a, 1%" dia. x 1" long overall. Theextruding inlet was provided with a frusto-conical mouth sloped at anangle of about 45 and of a depth b, which measured 0.5". The length 12of the straight cylindrical throat c was /a", and the surfaces of boththe inlet and throat were ground and polished to a high finish, thefinished diameter of throat 0 being 0.6 25. In the finishing operation,the extruding outlet was shaped to an outwardly expanding taper g of2-5", the degree of taper within the limits given being rathernon-critical.

It was found that the best compaction in manufacture was obtained bypressing the nibs first into the shape of FIG. 1, in which they werealso sintered and interalloyed, and thereafter machining them into theshape of FIG. 1a. The profile f bell mouth shown in FIG. 1 is actuallythat formed by two concentric frusto-conical surfaces, the outer one ofwhich is inclined to the horizontal at an angle a= whereas the inner oneis inclined to the vertical at an angle e=45. These two surfacesintersect in a toroidal surface which is formed to a radius f of 0.02",the lower extremity of which surface is located on the level of line x-xa distance d=% inwardly from the outside circumference of the nib bodyas pressed. The straight cylindrical throat of FIG. 1a measured 0.609"as rough-formed. The specific profile of bell-mouth described appears tobe particularly advantageous from the standpoint of ready disengagementof the compaction mold piston. As indicated in FIGS. 1 and 1a the top ofthe nib is ground oif on line x-x as a finishing operation to obtain thenib form of FIG. 1a.

The nib was formed by molding within a graphite die mold which, as shownin FIG. 2, comprises a cylindrical body 10 about 5 /2" in heightprovided centrally with, a bore 9 of the same size as the unfinishedoutside diameter of the die nib it is desired to form. Bore 9constitutes the mold cavity and is provided at the lower end with aclose-fitting annular graphite base plate 11 drilled centrally toreceive a solid cylindrical graphite core piece 12 of a diameter equalto that of the unfinished throat c of the nib to be formed. The bore isalso provided with a close-fitting plunger 17 formed at its lower endwith a concave surface which is the exact reverse configuration of thebell mouth of FIG. 1 which is to be formed in the nib. To permit easyrelative movement of plunger 17 axially with respect to core piece 12, aclearance of 0.001"-0.0015" is provided therebet-ween. Finally, a A;"diameter thermocouple well 18 is preferably provided in body 10.

In nib manufacture, it will be understood that a complete Weighed andmixed powder charge, dried to below about 3% moisture conent as amaximum, is first placed within bore 9, closed at the bottom by baseplate 11 and provided with core piece 12, if the die throat is to bepreformed. The charge is then tamped manually with the aid of plunger 17until enough powder has been introduced into the mold to produce a nibof the length desired. At this point the entire mold and its charge isplaced upright within a hydraulic press and pressure applied to plunger17 while base plate 11 is supported in place by the press platen and theentire die mold is heated, preferably by electric induction heating,until the alloying and sintering hereinbefore described is completed. Itis preferred to shield the die mold with two or more thicknesses ofasbestos paper wrapped circumferentially around the outside of body 10,and also on the top and bottom surfaces of the die mold, to preserveuniform temperature conditions within the die mold and, at the sametime, protect the mold from oxidation by the air.

A preferred procedure for the manufacture of die nibs of MoNSiZrOcomposition is to apply 1000 p.s.i. at room temperature, then heat themold with this pressure applied by electrical induction to a temperatureof about 1200 C. within about 8 mins. The pressure is then increased to2000 p.s.i. and heating continued under pressure to a temperature levelof about 1600 C., which requires an additional time of 5 mins. Then thepressure is increased to 3000 p.s.i. and the object maintained at thispressure and at a temperature of about 1600 C. for a soaking period of30 minutes. Thereafter, the temperature is increased to 1650 C. withinone minutes time and the pressure increased to 4000 p.s.1. A five minutesoak at the latter temperature and pressure completes the sintering, andheat and pressure are discontinued.

Core pin 12 is then removed from the hot mold by forcing it out with anarbor press, after which the hot mold, still containing the nib withinits cavity, is placed within a metal container which is loaded withalumina spheres. The mold is covered with the spheres, which shield themold from oxidation, and allowed to cool to room temperature, afterwhich the mold is placed in an arbor press and plunger 17 pusheddownwardly without support applied to the underside of base plate 11.This forces plate 11 and sintered nib 16 out of the bottom of thegraphite mold, after which the mold can be reloaded to make another nib.It will be understood that the mold and its appurtenances can be usedover and over again indefinitely.

The surface areas of the nib are belt-sanded and, thereafter, ground toparallel surfaces at top and bottom, as well as to desired height, usinga silicon carbide or diamond grinding wheel. The frusto-conical inletand the nib throat are then finished, both as regards surface qualityand dimensions. Finally, the nib is formed oircumferentially to fitwithin an elastic metal support housing as described in copending US.application S.N. 78,165, hereinbefore mentioned, after whichthe completedie is ready for hot metal extrusion service.

It is preferred to mold-form the nib throats at least to rough polishedstate, in the course of manufacture of the nibs themselves, because inthis way complete extrusion passages can be delineated by simplymachining the reverse configuration on the outside of the easilymachinable graphite core pin 12. One such intricate transverse throatprofile is that shown in FIG. 3, which was adapted to produce flutedextruded rods of copper, steel, tool steel and niobium. However, ifdesired, the nib extrusion passages can be formed by electrosparkmachining, diamond boning or ultrasonic machining.

The foregoing description is directed specifically to a single firingprocedure for the manufacture of compacts; however, it will beunderstood that a partly or fully reacted and allowed compact can bepulverized and resintered int-o absolutely sound compacts having all ofthe beneficial properties of this invention. This latter is sometimes anadvantageous procedure where the calorescence is so vigorous as toproduce blow holes in the original compact, since the complete physicalstructure is reconstituted in dense, homogeneous condition by the secondsintering.

The inherent lubricity and toughness possessed by compact made accordingto this invention is demonstrated by the following hot metal extrusiontests conducted with the specific die nib herein described in detail.This nib had a Rockwell A hardness of 85, 90, as measured in two spaceddeterminations, and a density of 4.82 gms./cm. The die design utilizedwas that shown in FIGURE 7 of US. application S.N. 78,165 hereinbeforementioned, which utilizes a ring housing enclosing the nibcircumferentially together with a separate base portion, drilledcentrally to clear the nib outlet, which supplies axial support for theconstruction. The ring housing was fabricated from a material whichdisplays a smaller thermal coefiicient of expansion over at least asubstantial portion of the temperature range involved than does themetal silicide nib. Thus, employing a relatively small interference fitin the cold assembly, the bonding joinder becomes tighter withtemperature rise. This contributes a progressively greater tangentialcompressive stress with rise in temperature, so that the sum of nibtensile strength plus tangential compressive stress is sufficient tooffset the disruptive loading imposed on the nib by hot metal extrusion.A suitable material of construction for the ring housing is Ferro-Tic C,a product of the Sinter Cast Division, Chromalloy Corporation, whichconsists of titanium carbide grains cemented together with a steelbinder. This material has a modulus of elasticity of 44 mm., which isadvantageous in that there is good stress transfer from nib to housingas a separate feature. The nib was assembled within the housing by pressfit at room temperature utilizing a 1 reducing taper in the direction ofmetal extrusion for both nib and housing, and an 0.008" diametricalinterference between the parts.

This die was utilized for the hot extrusion of four different materialsin the sequence hereinafter recited Without the use of any lubricantswhatever. The reduc tion ratio was 4.5 to 1 in all instances, by whichis meant the ratio of cross-sectional area of billet fed to extrudateproduct. The term nib washout refers to progressive enlargement of thenib mouth occurring as a consequence of extrusion.

A. The extruded material was brass analyzing 61.5% Cu, 35.5% Zn, 3% Pb,the billets fed measuring 1 dia. x 1 /2" long. These were preheated to1350 F. and the die itself was preheated to 850 F. to safeguard againstchilling the metal fed.

Two extrudate rods were made, both of which had high surface quality.There was no nib washout, nor any damage to the die.

B. The extruded material was metallic copper analyzing 99.9% pure, whichwas fed in as billets measuring 1 i dia. x 1 /2" long, preheated to 1500F., with the die preheated to 850 F.

Two extrudate rods were made, each having high surface quality, withoutany perceptible nib washout or damage to the die.

C. The extruded material was A.I.S.I. 1018 steel having the generalanalysis 0.15O.20% C, 0.600.90% Mn, 0.040% (max.) P, 0.050% (max.) S,balance Fe. The steel was fed as billets measuring 1 dia. x 1 /2 long,preheated to 2100 F., and the die was preheated to 850 F.

Two extrudate rods were formed, each of which had high surface quality,and there was no accompanying nib washout or die damage.

D. The extruded material was a niobium alloy analyzing 10% Ti, 10% Moand 80% niobium. This was fed to the die as a billet measuring 1%," dia.x 2 /2" long, preheated to 2700 F., the die being preheated to 1100 F.

A single extruded rod was formed approximately 10" long, which had agood surface quality, and there was no accompanying nib washout or diedamage.

From the foregoing, it is apparent that compacts made according to thisinvention possess remarkable inherent lubricity and toughness, whichmakes it possible to extrude metal billets having temperatures up toabout 6000 F., where suitably cooled die nibs are employed or,alternatively, where the extrusion is conducted at a high enough rate tocomplete it before there is destructive heat transmission to the die.

Extensive metallographic study under magnifications of 100-l000 onsections taken from die nibs and tool bits prepared in accordanceherewith has shown a microstructure such as that of FIG. 4, which isthat of an etched 11 50 15% HNO HF, balance H O ctchant) specimen at1000 taken from a die nib of the specific composition hereinbeforereported. The compact is seen to consist of two essential phases, thefirst, denoted p, being a white, hard, continuous phase having anapproximate 1200 Knoop hardness at 100 gms. load, abbreviated 1200 Kwhereas the second, denoted q, is a softer (ca. 600 K black,discontinuous phase which is vitreous in nature. A fine-grainedmicrostructure in the compact also appears to be beneficial, e.g., 110micron size with an average grain size of 5 microns. From this lastfact, it is seen that virtually no grain growth occurs during the hotpressing-sintering, the initial milled powders falling in the same 1-5micron particle size.

One theory which can be postulated is that the dark vitreous phasebecomes progressively less viscous as the temperature is raised, whilestill being retained in situ by the hard, strong, rigid matrix, so thatit affords a lubricating action against sliding contact with thecompact. Regardless of the true explanation, however, there is anestablished high-order lubricity evidenced during extremely severetests, such as those represented by the hot metal extrusions described.

A statistical appraisal of sample performance in all aspects, extendingfrom ease of hot-pressing, e.g., avoidance of sticking in the mold,elimination of cracking and the like, through mounting die nibs in theirholders, e.g., toughness and strength in resisting the stresses appliedat this stage, to final performance as hot metal extrusion diesindicates that ZrO is generally superior as an additive to either ZNO orCr O However, the demands of particular installations are so diverse andspecialized that the latter two metal oxides can well have uniqueapplications exclusive to each.

The ability to form intricately shaped compacts, such as the aperturednib hereinbefore utilized as the prime example for purposes of thisdescription, is an exceedingly important consideration. Industrial usagedepends to a large extent on the ease with which objects can be shaped,and compacts according to this invention can be made in sprerical formas well as with a variety of shapes, curved surfaces and the like. Itwill be understood that it is often times not necessary to prepare adie, bearing or similar structure as a unitary object, but that it canbe fabricated as a multiplicity of interfitting segments which, inassembly together, make up the entirety. Such a design approach isentirely feasible in view of all of the desirable physicalcharacteristics of the compositions of this invention.

From the foregoing, it will be understood that relative ly widemodifications can be made in composition, manufacturing pressures,temperatures and other factors without departure from the essentialspirit of this invention, and it is intended to be limited only by thescope of the following claims.

What is claimed is:

1. A powder metallurgy composition useful in the fabrication of shapedobjects having high inherent lubricity and toughness consistingessentially of 2053% Si, 40-65% Mo, l19% N and from about 520% of ametal oxide taken from the group consisting of ZrO ZnO and Cr O whereinthe size of all particles is less than about microns and of which atleast 75% by weight are less than about 5 microns.

2. A powder metallurgy composition useful in the fabrication of shapedobjects having high inherent lubricity and toughness according to claim1 wherein said metal oxide consists substantially solely of ZrO 3. Apowder metallurgy composition useful in the fabrication of shapedobjects having high inherent lubricity and toughness consistingessentially of 2053% Si, 40-65% Mo, 1l9% N and from about 520% of ametal oxide taken from the group consisting of ZIO2, ZNO and Cr Owherein the content of inert substances commingled therewith is lessthan about 5% by weight and the size of most particles therein isbetween about 1-3 microns with the maximum particle size about 10microns.

4. As a manufacture, a shaped object having a high having high inherentlubricity and toughness comprising concurrently heating and pressing apowder mixture consisting essentially of 20-53% Si, 4065% Mo, 119% N andfrom about 520% of a metal oxide taken from the inherent lubricity andtoughness comprising a powder 5 group consisting of ZrO ZnO and Cr Owherein the metallurgy composition sintered and alloyed to a substansizeof all particles is less than about 75 microns and of tially homogeneouscomposite; said powder metallurgy which at least 75% by weight are lessthan about 5 composition consisting essentially of 2053% Si, 40-microns, in a staged sequence consisting of maintaining 65% Mo, 119% Nand from about 5-20% of a metal a pressure of about 1000 psi. whileheating said powder oxide taken from the group consisting of ZrO ZnO, 1mixture from room temeprature to about 1200 C., then and Cr O whereinthe size of all particles is less than increasing the pressure to about2000 psi. and maintainabout 75 microns and of which at least 75% byweight ing this last-mentioned pressure while raising the temare lessthan about microns. perature to about 1600 C., then increasing thepressure 5. A composition useful in the fabrication of shaped to about3000 psi. while maintaining the temperature at objects consistingessentially of 53% Si, 65% 15 about 1600 C. for a period of about 30minutes, and Mo, 1l9% N and from about 520% of a metal oxide then,finally, raising the temperature to about taken f the group consisting fZIOZ, 0 and @203, while maintaining the pressure at about 4000 p.s.1.for a wherein the size of all particles is less than about E of aboutmlmlte? t9 efiect cofnpletlon 0f the microns and of which at least 75 byweight are less smtenng and alloymg of sald Powder mlxture' than about 5microns. 20 v 6. A composition of claim 5 in which the metal oxideReferences cued m the file of thls Patent consists substantially solelyof ZrO UNITED STATES PATENTS 7. A shaped object of claim 4 in which themetal 2,866,259 Bechtold Dec, 30,1958 oxide consists substantiallysolely of ZrO 25 2,878,113 Bechtold Mar. 17, 1959 8. A method for themanufacture of shaped objects 2,982,619 Long May 2, 1961 UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,110,091

November 12, 1963 Ernest L, Little, Jr, et al3 It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 9,

a line 2, after "size" insert below 10, line 10, for temeprature readtemperature Signed and sealed this 5th day of May 1964.,

(SEAL) Attest:

ERNEST W, SWIDER 3 column EDWARD Je BRENNER Attesting OfficerCommissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No, 3 1lO O9l November 12 1963 Ernest L. Little, Jr. 9et a1 It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent should readas corrected belo C iolumn 9, line 2 after "size" insert below column 10line 10, for "temeprature" read temperature Signed and sealed this 5thday of May 1964.

(SEAL) Attest:

ERNEST Wc SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A POWDER METALLURGY COMPOSITION USEFUL IN THE FABRICATION OF SHAPEDOBJECTS HAVING HIGH INHERENT LUBRICITY AND TOUGHNESS CONSISTINGESSENTIALLY OF 20-53% SI, 40-65% MO, 1-19% N AND FROM ABOUT 5-20% OF AMETAL OXIDE TAKEN FROM THE GROUP CONSISTING OF ZRO2, ZNO AND CR2O3,WHEREIN THE SIZE OF ALL PARTICLES IF LESS THAN ABOUT 75 MICRONS AND OFWHICH AT LEAST 75% BY WEIGHT ARE LESS THAN ABOUT 5 MICRONS.
 8. A METHODFOR THE MANUFACTURE OF SHAPED OBJECTS HAVING HIGH INHERENT LUBRICITY ANDTOUGHNESS COMPRISING CONCURRENTLY HEATING AND PRESSING A POWDER MIXTURECONSISTING ESSENTIALLY OF 20-53% SI, 40-65% MO, 1-19% N AND FROM ABOUT5-20% OF A METAL OXIDE TAKEN FROM THE GROUP CONSISTING OF ZRO2, ZNO ANDCR2O3, WHEREIN THE SIZE OF ALL PARTICLES IS LESS THAN ABOUT 75 MICRONSAND OF WHICH AT LEAST 75% BY WEIGHT ARE LESS THAN ABOUT 5 MICRONS, IN ASTAGED SEQUENCE CONSISTING OF MAINTAINING A PRESSURE OF ABOUT 1000P.S.I. WHILE HEATING SAID POWDER MIXTURE FROM ROOM TEMPERATURE TO ABOUT1200*C., THEN INCREASING THE PRESSURE TO ABOUT 2000 P.S.I. ANDMAINTAINING THIS LAST-MENTIONED PRESSURE WHILE RAISING THE TEMPERATURETO ABOUT 1600*C., THEN INCREASING THE PRESSURE TO ABOUT 3000 P.S.I.WHILE MAINTAINING THE TEMPERATURE AT ABOUT 1600*C. FOR A PERIOD OF ABOUT30 MINUTES, AND THEN, FINALLY, RAISING THE TEMPERATURE TO ABOUT 1650*C.WHILE MAINTAINING THE PRESSURE AT ABOUT 4000 P.S.I. FOR A PERIOD OFABOUT 5-6 MINUTES TO EFFECT COMPLETION OF THE SINTERING AND ALLOYING OFSAID POWDER MIXTURE.